Process of purifying resorcin



v1 ICI Feb 27, 1923..

al 5 5 ,s F0 L .l

N, .C R 0 V1.8 E. AnRw Wdw SN, 0,13 1|, SHI. SMC mum n Dl l D NWN r Fra S TS. E CA O DH DI MHT/V555."

' higher yield,

Patented Feb 27, lllZo CilElfll'CAL COVILANY, XNC., OF BROOKLYN, NEV

' naar roar..

Application filed December To all whom` t may cmwefm: y

Beit known that l, THURsToN N. Dissos- WAY, a citizen of the United States, residing at Flatbush7 Brooklyn borough, county of Kings, city of N ew York, and State of New York, have invented a new and useful lmprovement lin lDrocesses of Purifying llesorcin, olf which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this spe'ciic-ation.

yln the preparation of pure resorcin from the technical or impureproduct, the best known and usually practiced process is to crystalliae the impure product trom some solvent, such as alcohol, and recrystallize, it

until a product meeting the requirements is obtained. This process is not satisfactory, in that it is uneconomical; the yield not nearly approaching a quantitative one, and' much of the solvent being lost.

rlhe object of my invention isV to secure a to avoid the expense ot loss of solventi, and to secure 'a product ot' at least equal purity and better keeping qualinecessary,

ties.

Thehrst step of my intproved process contemplates la partial purification .of the resorcin, involving the elimination from the resorc'in oit certain impurities, particularly phenol and catechol. Both these impurities are almost invariably present in the product that is sold as technical resorcin.

The impure resorcin is placed in a suitablevessel and dissolved by the aid of heat in alittle water. ln treating further batches of resorcin, the liquor from a previous puriiication will be employed. 'l` he temperature is maintained below 100O C., preferably about 900 C.

After standing for an hour or two the solution is transferred to a c-rystallizing vessel. is preferred to use a stone crock 'that can be cooled in a. water bath. rl`he solution is stirred occasionally while the crystals are separating.

W' hen thoroughly cold the crystals are removed in a. ntriin'uge and dried below 100O C. l

rlhe mpst satisfactory purification is obtained it the process is so conducted that about 50% to 00% of the total resorcin in the hot liquor is recovered.

'l he mother liquor' of the crystals can be used a number ot times for the purification- YORK, A CORPORATION 0F 13, 1920. Serial No. 430,413.

of additional batches or the impure product.

The number of times that the liquor is usable depends, oit course, on the comparative purity of the product started with.' A run with a good quality ot technical resorcin gave the following results. I

The liquors were used twenty-two times and from' 3500 pounds ot the technical product pounds of crystals suitable for sublimation. The mother liquors should have contained about 200 pounds ot resorcin less certain impurities inthe technical-product and `mechanical losses. rlhese liquors were diluted with water until further dilution with water caused no appreciable precipitation, and the clear liquor was separated from the precipitate formed and concentrated in a still to the crystallizing point. rThis treatment yielded an additional seventy pounds of crystals suitable for sublimation.

ln place of the above purifying process, lthe following procedure may be adopted. -Tlieresorcin is ground to a coarse powder, packed in a percolator, and sufficient cold benzol is added to cover the powder. Alter standing for a few hours the phenol and catechol dissolve in the benzol. The solution is ythen drawn off. rThe solution remaining in the resorcin is then displaced by further addition ot benzol. After draining off the wash, the powder is removed from the percolator, spread on trays or pans away from flame. anddried at a temperaturevbelow 100O l. to remore the last traces of benzol.

The last described method of purification forms the subject-matter ot another application tiled ot even date herewith, `Serial No. 430,417.

'"lhe crystals obtained by the purifying treatment are then sublimed at a temperature sufficiently low to avoid decomposition of the resorcin. lin carrying out this part of theprocess, l prefer to use the apparatus illustrated in the accompanying drawing* which is a diagrammatic longitudinal vertical sectional view.

Over the burners a is a heat-ing chamber Zi, in which are placed pans c containing the partially purified .resorcin crystals. Beyond the heating chamber o and in tree communicationtherewith is a much larger condensing chamber al'. A pipe e connects the rear end of the condensing chamber with 'the the latter frees the bulb wholly or partially from contact therewith, and the temperature is then largely av matter of guess work. It is found, hoWeyer, that if the thermometer (il.) be suspended in the heating chamber, above the material, and preferably near the eXit'of the heating chamber, the temperature of the vapor, and incidentally of the material, may be maintained vapor at this point be maintained between 115435O C., sublimation may be efficiently carried on. Below the minimum of this range, the process is too slOwto be economical. Above the maximum of this range, dise coloration is' produced, especially toward the end of the process It is distinctly preferred to maintain the temperature between 125 and 1300"(1, this producing a high yield of superior quality and with suflicient rapidity to satisfy the requirements of economy.

During the process the resorcin vapor .driven off largely condenses in the chamber d. Uncondensed vapor returns through pipe c' to the heating chamber b'.

The operation may continue for the larger part of twenty-four hours. Assuming that twenty-eight pounds of resorcin crystals are placed in the pans, from fourteen to twenty pounds of resorcin will have beenv sublimed at the end of this period.

To the residue in the pans (consisting mainly of resorcin) are then added fresh resorcin: crystals in an amount (say) about equal to the quantity sublimed, and the operation is repeated. rlhe operationl may be repeated a number of times until the residue remaining in the pansconsists largely of impurities; such impurities, however, containing a substantial proportion of resorcin, which it is desirable to recover.

This resorcin is recovered by washing the pans with water, separating the solution of resorcin from insoluble matter, and recovering the resorcin either by extraction of the solution with an immiscible solvent, such as ether, or by concentration of the solution., preferably in a still, and crystallizationof the resorcin from the concentrated liquor.

From. the above description Ait will be observed that I obtain from 3500 pounds of resorcin approximately 3400 pounds of resorcin suitable for sublimation. Allowing for the loss, in the shape ofimpurities left in the subliming pans, and crediting the recovery of resorcin. from lthese impurities, I have found that, in the practice of the process on a commercial scale, approximately ninetyfive per cent of the resorcin contained in the impure product put in work'has been obi sub-tained as U. S. P. Resorcin. stantially constant. It is found that .if the The partial purification of the resorcin prior to sublimation is necessary only when the` resorcin. contains impurities, such as phenol and catechol,.which would be carried over, in thesublimation process, with the vapors of resorcin into the condensing chamber and contaminate the sublimed product. Inasmuch as thetechnical resorcins on Ithe market almost invariably contain such 4impurities, a previous purification is generally necessary.

Having now fully described my invention, what I claim and desire to protect by Letl ters Patent is:

1. The process of purifying resorcin which comprises sublimation of the resorcin and regulating the temperature by maintaining the vapors near the exit of the heating chamber above. about 115 degrees C., thereby insuring vaporization of a substantial part of rtween 125 and -130 degrees C., thereby insuri ing` the vaporization of the maximum peri centage of resorcin consistent with insurance against decomposition.

In testimony of which invention, I have hereunto set my hand, at Brooklyn, N. Y., on this tenth day of December, 1920.

THURTON N. DISSOSIVAY. 

